OK--you have reason to believe that you are (1) facing an imminent threat of death or serious bodily harm, and that (2) you have no choice but to employ deadly force to defend your self. That means that you have concluded that one or more violent criminal actors have the ability and the opportunity to harm you right now and that you are in jeopardy.
Most probably, you have someone close to you moving fast, and you have very little time not only to decide but to stop the assailant(s) before you are injured, and no realistic ability to optimize your "shot placement"'.
Think about it: do you really think that it would be even remotely possible for you to decide whether to shoot that attacker in the face or the groin or between the eyes if the situation really justified deadly force?
Don't rely upon a pelvic shot with a lower powered weapon; your objective is to stop, not kill, so even if you could be assured hitting the heart, that won't necessarily save you. You are going to have to hit wherever you can, very quickly, and most probably, repeatedly.
That's true with a .32 and with a .357 SIG. It's just that you have a better chance with the latter.
Yep--you can only shoot for what is commonly described as center mass, as fast as you can.